Aren't columnset powerful enought ?
From the manual
\usemodules[visual]
%% \definecolumnset[example][n=4]
%% \starttext
%% \startbuffer
%% \fakewords{100}{200}
%% \placefigure{}{\externalfigure[placeholder][width=\One]}
%% \fakewords{100}{200}
%% \placefigure{}{\externalfigure[placeholder][width=\Two]}
%% \fakewords{100}{200}
%% \stopbuffer
%% \startcolumnset[example]
%%    \definecolumnsethsize{example}{1}{1}\One
%%    \definecolumnsethsize{example}{1}{2}\Two
%%    \dorecurse{5}{\getbuffer}
%%    \dorecurse{10}{\fakewords{100}{200}\par}
%% \stopcolumnset
%% \stoptext


\definecolumnset[example][n=4]
\starttext
\startbuffer
\placefigure[tbrl]    {tblr}{\externalfigure[fake][width=\One, lines=5]}
\placefigure[fxtb:2*4]{fxtb}{\externalfigure[fake][width=\Two, lines=5]}
\placefigure[btlr]    {btlr}{\externalfigure[fake][width=\Two, lines=5]}
\placefigure[btlr]    {btlr}{\externalfigure[fake][width=\Three,lines=5]}
\dorecurse{5}{\fakewords{100}{200}\par}
\stopbuffer
\startcolumnset[example]
   \definecolumnsethsize{example}{1}{1}\One
   \definecolumnsethsize{example}{1}{2}\Two
   \definecolumnsethsize{example}{1}{3}\Three
   \dorecurse{4}{\getbuffer}
\stopcolumnset
\stoptext





%% \definecolumnset[example][n=4]
%% \starttext
%% \startcolumnset[example]
%% \placefigure[btlr]{brlr}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[btlr]{brlr}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[btrl]{btrl}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[btrl]{btrl}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[tblr]{tblr}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[tblr]{tblr}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[tbrl]{tbrl}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[tbrl]{tbrl}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[lrbt]{lrbt}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[lrbt]{lrbt}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[lrtb]{lrtb}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[lrtb]{lrtb}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[rlbt]{rlbt}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[rlbt]{rlbt}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[rltb]{rltb}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \placefigure[rltb]{rltb}{\externalfigure[fake][width=\textwidth,lines=3]}
%% \dorecurse{10}{\fakewords{50}{100}\par}
%% \stopcolumnset
%% \stoptext